Grieveson was convicted of their murders in 1996 and handed three life sentences, with a minimum tariff of 35 years.

He would have been eligible to be considered for parole in 2031, but the new term means this will not happen until 2048.

'Horrendous attack'

Sentencing him for Simon's murder, Mr Justice Ramsey said the schoolboy had "everything to live for".

"He came from a supportive family, of a father, a mother and a brother," he said.

"This was a horrendous attack and murder of an innocent young boy, groomed by you and lured for your sexual pleasure."

Speaking after the verdict, Dept Supt Roger Ford, of Northumbria Police, said: "Grieveson is a calculated serial killer whose actions left residents shocked and cast a shadow over the community for many years.

"We welcome this verdict and hope that Simon Martin's family and friends now feel that justice has been done."

Robert and Jean Martin, Simon's parents, said in a statement: "This is the end of a long journey for us, which will finally give us closure.

'Painful memories'

"No other family should have to lose a son and suffer the heartache we have had to endure."

The families of Grieveson's three other victims said in a joint statement: "Our sons were taken away from us by a cruel man whose despicable actions cost four boys their lives.

"Listening to this trial has brought back so many painful memories for us, and we would like to express our deepest sympathies to Simon's parents for the pain they have suffered over the last 23 years.

"We hope that the outcome of this trial will help them to feel that justice has been done for Simon.

"Our sons would be grown men now. We will never forget them and they will live on in our hearts forever."